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27" JVC tv model:AV-27320,chassis:A67

Discussion in 'Electronic Repair' started by Sidney, May 30, 2004.

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  1. Sidney

    Sidney Guest

    27" JVC stereo tv model:AV-27320,chassis:A67,year:Oct 2001.After the
    customer was watching tv for a few hours picture size kept shrinking
    all on all four sides down to a dot within a few seconds then the tv
    shut off and now only relay click followed by LED blinking.
    I found Q522=2SD2499=NTE2331 and F902=1.25 amp fuse to be open,I have
    not yet troubleshooted tv further anyone have any common repair tips
    for such a failure?.
    Thanks in advance for replies.

    Sidney
    Dartmouth,Nova Scotia
    Canada
     
  2. David

    David Guest

    Only tip, don't leave the NTE sub in that set as it won't last. The
    tolerances of the circuit require an EXACT replacement for Q552.

    Look for bad solder connections in the power supply and sweep to have caused
    the failure.

    David
     
  3. Jason D.

    Jason D. Guest

    Sidney,

    I service JVC sets daily (warranty/contract and customers'), Very
    rare horizotal failures. It depends on type of chassis.

    If this set uses STR30134 regulator, then replace horizontal
    transistor and redo all solder joints on all 1/2W and 1W resistors.
    (must be exact part preferably from JVC), check D421 and R421 is good
    if bad or fried, the vertical IC is fried then have to replace
    vertical parts: generic will do: flameproof 1.8 Ohm, 1/2W, jelly bean
    diode (RGP10J), LA7832 and 100uF 35V cap. This chassis with STR-30134
    also have cap for the horizontal transformer driver but it's well out
    of heat and right at the edge so there's not a problem.

    If this is doesn't fit what I described, uses SMPS only for both
    standby and run using (STRF-6626) then replace small 1uF 160V cap for
    the horizontal transformer driver +B filter and exact horizontal
    transistor. It is in middle of two hot resistors killing that cap's
    ESR. Resolder all 1/2W and 1W resistors still applies, watch out for
    dud vertical circuit.

    Good idea to see if you have resistance between HV suction and the
    ground pins on the flyback which is not supposed to be there. Also
    ring fly just in case. Fly for JVC is very occasionally found bad
    except for AV-32F702 series using flat CRT, it is somewhat high
    failure rate.

    Cheers,

    Wizard
     
  4. Sidney

    Sidney Guest

    Thanks David & Jason D.

    This tv belongs to a friend of mine who told me that Q522=2SD2499
    (HOT) was shorted but it is fine but F902 still open (LOL),he dropped
    it off to my shop and I rang the T502=FSM27A001 (QQH0028-001)=flyback
    transformer by using the calibration output of my TEK-465 oscilloscope
    but no ringing so upon troubleshooting I found that the 12v (D1543=RGP
    XXX) secondary supply off the flyback was loaded down to about 250
    ohms so I disconnected D1543 and problem still remains.
    I ruled out IC1541=AN7809F & IC1551=AN7805F and I rang the yoke
    unplugged and it rang good.
    Anyone know if the this flyback is a common failure? also what could
    be loading down the 12v source?.
    This tv uses IC1101=TB1253AN & IC1921=STR30134

    Sidney
    Darmouth,Nova Scotia
    Canada
     
  5. Jason D.

    Jason D. Guest

    Flyback removed from chassis and still won't ring? If yes that's it.
    Get both HOT and flyback from JVC, cost is not a problem, JVC is nice
    sets and lasts long time because of nice CRTs. While at it, change
    out 100uF 35V electrolytic on that vertical IC, they were always dried
    up by the vertical's heatsink intense heat and cap often were 85C.
    When you get it running, touch the U shaped sloped vertical heatsink.
    HOT!

    The 12V is used to supply these 9V and 5V regulators, also 12V is for
    the vertical I think along with typical 26V. Also via diode (forward
    biased) to the standby supply to "prop" up the standby supply once tv
    is running. This includes the relay and small 5V with reset regulator
    (5 legged thing) for micro.

    Tuner only use 33V and 5V stuff.

    By the way that jungle IC (TB1253AN) is digital controlled without
    503kHz crystal.

    The money maker was in JVC vertical frying because of that 100uF cap.
    :)

    Yes, that chassis have two fuses, one (I think 4A or 5A?) for before
    the diode bridge & cap and after the B+ regulator (uses 1.25A fast
    blow for sure.)

    Cheers,

    Wizard
     
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